The present invention relates to a loudspeaker, and more particularly to a damper provided in the loudspeaker.
A loudspeaker provided in an audio system is an electroacoustic device that converts an electric signal (electrical energy) into an acoustic signal (sound energy). ELectrodynamic loudspeakers, which are superior in quality of the reproduced sound and other properties are widely used today.
The loudspeakers are mounted in audio systems of various shapes, so that it is preferable to reduce the thickness of the speaker as much as possible.
FIGS. 4a and 4b are a plan view and a sectional view showing a main part of a conventional electrodynamic loudspeaker, respectively. Referring to the figures, the conventional electrodynamic loudspeaker has a yoke 103, magnet 102 mounted on the yoke 103, and a pole piece 101 mounted on the magnet, thereby forming a magnetic circuit including an annular magnetic gap.
The magnetic gap is formed between the pole piece 101 and the yoke 103, the distance there-between being maintained substantially constant along the entire length. A frame 104 made of such a material as a resin is attached to the yoke 103 along the outer periphery thereof, thereby forming a frame assembly as well as the magnetic circuit.
A conical diaphragm 105 having a center hole is mounted above the pole piece 101. The outer periphery of the diaphragm 105 is secured to the frame 104 through an edge 106 attached to the frame.
A cylindrical voice coil bobbin 108a is provided in the hole of the diaphragm 105, the upper periphery attached thereto. A voice coil 108 is mounted in a space between the yoke 103 and the pole piece 101, surrounding the bobbin 108a. 
The voice coil bobbin 108a is supported by the frame 104 through a damper 107. The damper 107 resiliently supports the diaphragm 105 held by the edge 106, voice coil 108 and the voice coil bobbin 108a at the respective predetermined positions, and further suspensively supports the voice coil 108 within the magnetic gap.
In order to reinforce the diaphragm 105, a cap 110 is mounted on the center portion of the diaphragm 105, so as to cover the center hole thereof.
The ends of the voice coil 108 are directed out of the coil bobbin 108a so as to be connected to leads 108b. Each lead 108b is securely mounted on the outer wall of the voice coil bobbin 108a and on the upper surface of the diaphragm 105 by an adhesive A. Each lead 108b further passes through the diaphragm 105 to the underside thereof, and is electrically connected to a terminal 109 provided on the frame 104.
In the thus constructed loudspeaker, when applied with driving current through the terminals 109, the suspended voice coil 108 generates a driving force. The driving force renders the voice coil bobbin 108a to vibrate the diaphragm 105, thereby generating sounds.
Since the diaphragm 105 is deflected in the driving direction in operation, in order to prevent the diaphragm 105 from tensing and being exerted with a load, it necessary for each of the leads 108 to have a sufficient length between the diaphragm and the terminal 109 to keep the lead lax.
However, when the length of the lead 108b is long, due to the natural frequency thereof, the lead 108b may be deflected in a direction opposite from the moving direction of the diaphragm 105 and the damper 107 during the operation. As a result, the leads 108b collide against the diaphragm and the damper, thereby giving a shock. Consequently, a noise may be generated in the reproduced sound, and the lead 108 may be cut off.
In order to prevent such an accident, a sufficient space is needed between the diaphragm 105 and the damper 107 so that the leads 108b do not contact either of them. As a result, the thickness of the loudspeaker in the driving direction of the diaphragm is increased so that there is a limit in rendering the loudspeaker thin.
An object of the present invention is to provide a loudspeaker having a reduced thickness wherein the lead is prevented from colliding against the diaphragm and the damper.
According to the present invention, there is provided a loudspeaker having a cylindrical frame, a magnetic circuit formed on the frame, a voice coil disposed in a magnetic gap of the magnetic circuit, a diaphragm, comprising, a damper attached to the frame and supporting the voice coil, and leads connected to both ends of the voice coil, the leads being attached to the damper from an inner portion to an outer portion by stitching.
The present invention further provides a loudspeaker having a cylindrical frame, a magnetic circuit formed on the frame, a voice coil disposed in a magnetic gap of the magnetic circuit, a diaphragm, comprising, an annular damper attached to the frame at an outer periphery and connected to the voice coil at an inner periphery so as to support the voice coil in a floating state, leads connected to both ends of the voice coil, the leads being attached to the damper from an inner portion to an outer portion by stitching.
The damper has a corrugated sectional shape, and each of the leads is spirally disposed on the damper.